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Tuning and Probing the Distribution of Cu+ and Cu2+ Trap States Responsible for Broad-Band Photoluminescence in CuInS2 Nanocrystals.
ACS Nano ( IF 15.8 ) Pub Date : 2018-10-31 , DOI: 10.1021/acsnano.8b05843 Ward van der Stam 1 , Max de Graaf 1 , Solrun Gudjonsdottir 1 , Jaco J Geuchies 1 , Jurgen J Dijkema 1 , Nicholas Kirkwood 1 , Wiel H Evers 1 , Alessandro Longo 2, 3 , Arjan J Houtepen 1
ACS Nano ( IF 15.8 ) Pub Date : 2018-10-31 , DOI: 10.1021/acsnano.8b05843 Ward van der Stam 1 , Max de Graaf 1 , Solrun Gudjonsdottir 1 , Jaco J Geuchies 1 , Jurgen J Dijkema 1 , Nicholas Kirkwood 1 , Wiel H Evers 1 , Alessandro Longo 2, 3 , Arjan J Houtepen 1
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The processes that govern radiative recombination in ternary CuInS2 (CIS) nanocrystals (NCs) have been heavily debated, but recently, several research groups have come to the same conclusion that a photoexcited electron recombines with a localized hole on a Cu-related trap state. Furthermore, it has been observed that single CIS NCs display narrower photoluminescence (PL) line widths than the ensemble, which led to the conclusion that within the ensemble there is a distribution of Cu-related trap states responsible for PL. In this work, we probe this trap-state distribution with in situ photoluminescence spectroelectrochemistry. We find that Cu2+ states result in individual "dark" nanocrystals, whereas Cu+ states result in "bright" NCs. Furthermore, we show that we can tune the PL position, intensity, and line width in a cyclic fashion by injecting or removing electrons from the trap-state distribution, thereby converting a subset of "dark" Cu2+ containing NCs into "bright" Cu+ containing NCs and vice versa. The electrochemical injection of electrons results in brightening, broadening, and a red shift of the PL, in line with the activation of a broad distribution of "dark" NCs (Cu2+ states) into "bright" NCs (Cu+ states) and a rise of the Fermi level within the ensemble trap-state distribution. The opposite trend is observed for electrochemical oxidation of Cu+ states into Cu2+. Our work shows that there is a direct correlation between the line width of the ensemble Cu+/Cu2+ trap-state distribution and the characteristic broad-band PL feature of CIS NCs and between Cu2+ cations in the photoexcited state (bright) and in the electrochemically oxidized ground state (dark).
中文翻译：
调整和探究负责CuInS2纳米晶体中宽带光致发光的Cu +和Cu2 +陷阱态的分布。
在三元CuInS2（CIS）纳米晶体（NCs）中控制辐射复合的过程已经引起了激烈的争论，但是最近，几个研究小组得出了一个相同的结论，即光激发电子在一个与铜有关的陷阱态上与一个局部空穴重组。此外，已经观察到单个CIS NCs显示的光致发光（PL）线宽比集合体窄，从而得出结论，集合体中存在与PL有关的Cu相关陷阱态的分布。在这项工作中，我们用原位光致发光光谱电化学方法研究了这种陷阱态分布。我们发现Cu2 +状态导致单个的“暗”纳米晶体，而Cu +状态导致“明亮的” NCs。此外，我们表明我们可以调整PL的位置，强度，通过从陷阱态分布中注入或去除电子，以循环方式改变线宽和线宽，从而将包含“暗” Cu 2+的NC的子集转换为包含“亮” Cu +的NC，反之亦然。电子的电化学注入导致PL的变亮，变宽和红移，这与激活从“深色” NC（Cu2 +状态）到“明亮” NC（Cu +状态）的广泛分布和激活的激活相一致。集合陷阱态分布内的费米能级。对于将Cu +态电化学氧化为Cu2 +观察到相反的趋势。
更新日期：2018-10-29
中文翻译：
调整和探究负责CuInS2纳米晶体中宽带光致发光的Cu +和Cu2 +陷阱态的分布。
在三元CuInS2（CIS）纳米晶体（NCs）中控制辐射复合的过程已经引起了激烈的争论，但是最近，几个研究小组得出了一个相同的结论，即光激发电子在一个与铜有关的陷阱态上与一个局部空穴重组。此外，已经观察到单个CIS NCs显示的光致发光（PL）线宽比集合体窄，从而得出结论，集合体中存在与PL有关的Cu相关陷阱态的分布。在这项工作中，我们用原位光致发光光谱电化学方法研究了这种陷阱态分布。我们发现Cu2 +状态导致单个的“暗”纳米晶体，而Cu +状态导致“明亮的” NCs。此外，我们表明我们可以调整PL的位置，强度，通过从陷阱态分布中注入或去除电子，以循环方式改变线宽和线宽，从而将包含“暗” Cu 2+的NC的子集转换为包含“亮” Cu +的NC，反之亦然。电子的电化学注入导致PL的变亮，变宽和红移，这与激活从“深色” NC（Cu2 +状态）到“明亮” NC（Cu +状态）的广泛分布和激活的激活相一致。集合陷阱态分布内的费米能级。对于将Cu +态电化学氧化为Cu2 +观察到相反的趋势。
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